In many applications, the safe coupling of connectors is of high importance. For example, in the case of car safety systems, as e.g. airbag systems in passenger cars, the connectors used for the connection of an airbag to its ignition base have to be provided with reliable safety systems. To ensure that the connectors cannot become loose unintentionally, secondary locking members are used to guarantee the safe mechanical coupling.
An example of a connector with a secondary locking member is described in the WO 97/41623 A1. This document describes a connector 20 which can be mated with a corresponding counter-connector being part of an airbag ignition mechanism. In assembled condition, when the connector is mated with the corresponding counter-connector, it is fixed to the counter-connector by means of flexible latching arms. During mating of the connectors, these arms are deflected and snap back into corresponding latching clearances of the counter-connector, when fully mated. For securing the mechanical coupling of the connectors, the WO'623 suggests a secondary locking member which can be inserted into the connector when the two connectors are mated. The secondary locking member comprises locking arms, which upon insertion of the secondary locking member move between faces of the counter-connector housing and the latching arms of the connector. Once the locking arms are inserted, they inhibit bending of the latching arms. Thus, the latching arms cannot bend out of the latching clearances and the mechanical coupling of the connectors is secured. The secondary locking member described in WO'623 is further provided with locking means to fix the secondary locking member in its locking position, which is the above described position in which it secures the connector mating. However, in the case described in the WO'623, it is possible to place the secondary locking member in a half-fitting position, in which it may not function properly and in which it is not fixed to the connector, and therefore can be removed unintentionally.
A further development of a secondary locking member is disclosed in the co-owned patent application DE 100 05 858 A1. This document discloses a connector with a secondary locking device and a safety spring element, which serves to hold the secondary locking member in a pre-locked position, in which the secondary locking member is mounted to the connector housing but does not hinder mating or unmating of the connector with a corresponding counter-connector. The safety spring element described in the DE'858 further provides a so-called go/no go function for the secondary locking member: In the pre-locked position of the secondary locking member, two spring arms of the safety spring element are in contact with stop shoulders of the secondary locking member, thereby preventing a movement of the secondary locking member in direction towards its locking position. Upon mounting of the connector to a corresponding counter-connector, the counter-connector housing comes into contact with a releasing portion of the connector housing, thereby pressing this releasing portion against the safety spring element. By this pressing action, the safety spring element is deformed and the two spring arms are freed from the stop shoulders of the secondary locking member. Upon consequent moving of the secondary locking member towards its locking position, each spring arm is guided by an inclined channel of the secondary locking member, thereby being bent and biased against the edge of this inclined channel. Shortly before the secondary locking member is placed in its locking position, each spring arm passes a turning point of the inclined channel and snaps into a notch of the secondary locking member, thereby fixing the secondary locking member in its locking position. As long as the secondary locking member is not placed in this locking position, the spring arms are biased against the edges of the inclined channel, and due to the resulting restoring spring force they inhibit the secondary locking member to be placed in a half-fitting position unintentionally: i.e. the spring force causes the secondary locking member to move back into its pre-locked position. The safety spring element thereby provides a go/no go mechanism for the secondary locking member, which assures that the secondary locking member is either placed correctly in its locking position or is moved back into its pre-locked position, but prevents any intermediate position.
A similar mechanism is described in the co-owned WO 2012/055719 A1.